Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing a first image in the sequence; and,

FIG. 2 is a front view of a second image in the sequence thereof.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-2. The process or period in which one image transitions to another forms no part of the claimed design.

The broken line showing of a display screen or portion thereof, and portions of the transitional graphical user interface form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 